Piston expander



May 16, 1939. c. c. CRAVEN PISTON EXPANDER Filed March 23, 1956 I INVENTATTORNEYS.

- 25 Figure 1 is a front elevation of a piston expand- Patented May 16,1939 PATENT mm PISTON EXPANDER.

Gland C. Craven, Kansas City, Mo., assignor to A. B. Chance (10.. acorporation Application March 23, 1936, Serlal'No. 70,243

2 Claims.

This invention relates to piston expanders and particularly to a pistonskirt expander wherein a resilient member is adapted to exert pressurein opposite directions against the marginal walls of the split of apiston skirt.

' The principal object of this invention is the provision of unitarystructure adapted to .engage and force apart the marginal edges of theslot formed in the skirt of a piston whereby said skirt is expanded.Another object of the invention is the provision of a resilient,U-shaped piston expander having a transversely disposed lug adjacenteach of the free ends thereof formed to project into and se- 5 curelyengage the marginal edges of a slot formed in the piston skirt.

Other objects of the invention are econoifiy and simplicity ofconstruction, ease of installation, and the provision of means wherebythe expander securely engages the skirt.

With these and other objects which will appear1 during the course ofthespecification in view, reference'will now be had to the drawing,wherein: I

or embodying this invention.

Fig. 2 is a side elevation of the same. Fig. 3 is an outside view of aportion of the skirt of a piston, showing the expander in the operativeposition.

Fig. 4 is a vertical section, taken on line IV-IV of Fig. 3. o

Fig. 5 is an inside elevation of a portion of the piston skirt, showingthe expander in the oped ative position, and, Fig. 6 is afragmentary,'cross sectional view taken on line VI-VI of Fig. 3.

Like reference characters designate similar parts throughout the severalviews, and the nu-" meral It) represents a portion of the skirt of apiston, provided with a slit or slot I2 that extends from the open endof the skirt to 'a point adjacent the sealing portion or head of thepiston. The margins or side walls M of the -slit are provided withoppositely disposed receiving orifices l6 which are' substantiallysymmetrical at opposite sides of the slit. These orifices combine toproduce a" substantially frusto-conical holethrough the skirt, with thelarger crosssectional area at the outside thereof, thus forming inwardlyconverging side walls for reasons hereinaiterset forth.

Referring now particularly to the expander which is shown in its normalform in Figs. 1 and 5 2, it will be observedthat it comprises a singlestrip of resilient sheet metal ll which is rebent upon itself into asubstantially U-shaped body portion 20, the arms 22 of which areslightly bowed inwardly as at 24. Extending in like direction and intransverse relation to 20, adjacent 5 the free end of each of the arms22, is 9. lug 28. Each lug is substantially semi-circular in crosssection and semi-frusto-conical in a plane'perpendicular to arm 22.

With reference to Figs. 3, 4, 5 and 6, in which 10 the expander isshownin the operative ,position in the piston Skiltyit will be notedthat these lugs 26 are adapted to be fitted into orifice l6 so as toconform to the inner walls thereof insuch a manner as to preclude anyaccidental removal of 15 the expander from its operative position. When,.the expander is to be positioned in the opening formed throughtheskirt, the arms 22 are compressed' sufllciehtly to allow the lugs to.be, introduced from the inside of the piston through 20 the small sideof the opening, after which they are permitted to be 'forced outwardlyagainst the side walls by the action of the tension set up -in.the bodyof the expander. When so positioned, 'points 2i of the two arms willbe-in contact, 25

thereby shortening the fulcrum lever of lugs 26 to produce a muchgreater pressure against the opposite walls of slit 12 than could beobtained 'with the fulcrum at the closed end of the U- shaped bodyportion. I x 3 As a further means to facilitate proper tensioning of thelugs for expanding the piston skirt,

arms 22 are tapered from their greatest width at the closed end of body20 to their'narrowest width at their free end.- That portion 28 at the35 free end of each of the-armswhich extends beyond lugs 26 serves tocontact the innerwall of the piston skirt to prevent undesirable rockingof the body portion. i

The undercut relation of the lugs and the side 6 walls of the conicalhole in the skirt of the piston is such that it becomes necessary tocompress the outer ends of arms 22. to a considerable degree before theexpander can be released from its operative position. This feature isveryimpor-- 45 tent and insures the proper relation of parts withoutdanger of the expander becoming dislodged to cause interference with theproper action of the piston within the cylinder.

While I have shown the arms contacting at 2'4 50 in the drawing, itwould be possible to so construct the resilient portion of the expanderso as to produce the exact tensions necessary to obtain proper expansionunder all circumstances.

Having thus described theinvention, what I 5 v claim as new and desireto secure by Letters Patent is:

' 1. In combination; a piston comprising a head portion and a skirthaving a longitudinal slot therein forming opposed edge faces, each ofsaid faces having a notch therein extending transversely of saidlongitudinal slot, said notches being in opposed relation and combiningto create a frusto-conical orifice through the skirt of the piston withits largest diameter at the outer face of the skirt; and a sheet metalexpander comprising a resilient U-shaped body adapted to exert expandingforce against the opposed edge faces of the skirt, said body having alaterally extending lug on one edge of said body adjacent to each freeend thereof the remote faces of said lugs combining to present airusto-conical surface engageable with the said orifice of like formwhen the expander is in the operative position.

2. In combination; a piston comprising a head portion and a smrt havinga longitudinal slot areas therein forming opposed edge faces, each ofsaid faces having a notch therein extending transversely of saidlongitudinal slot, said notches being in opposed relation andcombiningto create a frusto-conical orifice through the skirt of the piston withits largest diameter at the outer face of the skirt; and a sheet metalexpander comprising a resilient U-shaped body adapted to exert expandingforce against the opposed edge faces of the skirt, said bodyhaving alaterally extending lug on one edge of said body adjacent to each freeend thereof, the remote faces of said lugs combining to present afrusto-conical surface engageable with the said orifice of like formwhen the expander is in the operative position, said lugs being inopposed relation and spaced inwardly from the free ends of said U-shapedbody whereby to prevent rocking movement of the body toward and from theskirt of the piston.

CLATUD C. CRAVEN.

